There is known a valve apparatus disposed in a fluid device such as a pump, and configured to adjust the flow rate of fluids supplied from the fluid device. FIG. 1 is a schematic diagram showing the related valve apparatus disposed in the fluid device.
As shown in FIG. 1, valve apparatus 1 includes valve box 5 including inlet 2, outlet 3, and valve seat 4. Valve seat 4 is disposed in valve box 5. Inlet 2 is connected to a pump not shown, and fluid 6 is supplied from the pump through inlet 2 to valve box 5. An opening is formed in valve seat 4, and fluid 6 that flows in from inlet 2 passes through the opening to flow to outlet 3.
Valve apparatus 1 further includes valve body 7 for opening/closing the opening of valve seat 4 in valve box 5. Valve body 7 is connected to actuator 9 via valve shaft 8, and actuator 9 moves valve body 7 to open/close the opening of valve seat 4.
The operation of valve apparatus 1 and the flow rate of fluid 6 flowing out from outlet 3 of valve apparatus 1 will be described, referring to FIGS. 2A to 2E and FIG. 3. FIGS. 2A to 2E illustrate the operation of valve apparatus 1, and FIG. 3 is a graph showing the time-sequential change of the flow rate of fluid 6 that flows out from outlet 3 of valve apparatus 1.
As shown in FIG. 2A, in a state in which the opening of valve seat 4 has been closed by valve body 7, fluid 6 does not flow out from outlet 3 (period P1 shown in FIG. 3). As shown in FIG. 2B, actuator 9 moves valve body 7 in a direction such that the opening of valve seat 4 is opened in order to increase the flow rate of fluid 6 from outlet 3 (period P2 shown in FIG. 3).
When the opening of valve seat 4 is opened and the movement of valve body 7 stops (FIG. 2C), fluid 6 flows out from outlet 3 at a certain flow rate (period P3 shown in FIG. 3). Actuator 9 moves valve body 7 in a direction for closing valve seat 4 from the state shown in FIG. 2C, and then the flow rate of fluid 6 that flows out from outlet 3 is reduced (FIG. 2D and period P4 shown in FIG. 3).
As shown in FIG. 2E, valve body 7 closes the opening of valve seat 4, and therefore no more fluid 6 flows from outlet 3 (period P5 shown in FIG. 3).
Actuator 9 is usually disposed outside valve box 5. In such a valve apparatus 1, as shown in FIG. 1, valve shaft 8 is inserted into through-hole 10 formed in the wall of valve box 5. Valve apparatus 1 includes sealing member 11 such as an O-ring or a V gasket for closing the gap between valve shaft 8 and through-hole 10. FIG. 4 is an expanded sectional view showing the periphery of through-hole 10 of valve apparatus 1 where the O-ring is used as sealing member 11.
As shown in FIG. 4, sealing member 11 consisting of the O ring is in contact with valve shaft 8. Accordingly, when valve shaft 8 moves, valve shaft 8 or sealing member 11 is easily worn. Wear debris generated by the abrasion of valve shaft 8 or sealing member 11 enters fluid 6, thus causing the fluid including the wear debris to flow out from outlet 3.
As technology to solve the problem, JP2011-33074A (hereinafter, referred to as “Patent Literature 1”) discloses an example of a valve apparatus that uses, as sealing member 11, a flexible film such as a diaphragm.
FIG. 5 is a schematic diagram showing valve apparatus 12 where a flexible film is used as a sealing member. Components similar to those shown in FIG. 1 are denoted by similar reference numerals, and will be described.
As shown in FIG. 5, valve apparatus 12 includes flexible film 13 disposed in through-hole 10. A hole is formed in flexible film 13, and valve shaft 8 is inserted into the hole. The peripheral edge of the hole of flexible film 13 is fixed to the outer periphery of valve shaft 8, and the outer peripheral end of flexible film 13 is fixed to the peripheral edge of through-hole 10.
In valve apparatus 12 disclosed in Patent Literature 1, flexible film 13 moves integrally with valve shaft 8. Accordingly, even when valve shaft 8 moves, valve shaft 8 is not worn, therefore wear debris is not generated. Thus, the incursion of impurities into fluid 6 can be prevented.